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Date: Mon, 17 Mar 2025 15:30:28 +0000
Message-ID: <CAO__Xv4END_NsATOGSnCArGuP_UmSpMxSMsSNPsQZnLooOWTsQ@mail.gmail.com>
Subject: Re: [PHP-DEV] RFC: short and inner classes
To: Rob Landers <rob@bottled.codes>
Cc: internals@lists.php.net
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On Wed, 5 Mar 2025 at 23:14, Rob Landers <rob@bottled.codes> wrote:

> Hello PHP Internals,
>
> I'd like to introduce my RFC for discussion:
> https://wiki.php.net/rfc/short-and-inner-classes
>
> This RFC defines a short class syntax as well as the ability to nest
> classes inside another class. This introduces an unprecedented amount of
> control, flexibility, and expressiveness over how objects are used and
> instantiated in PHP. There is a PR (
> https://github.com/php/php-src/pull/17895) that implements this
> functionality -- all test failures are related to different/new/incorrect
> error messages being generated. However, the core functionality exists to
> take for a test ride.
>
> So, what do I mean by "unprecedented amount of control"? With this change=
,
> you can declare an inner class as private or protected, preventing its
> usage outside of the outer class:
>
> class User {
>   private class Id {}
>
>   public function __construct(public self::Id $id) {}
> }
>
> In the above example, the class `User` is impossible to construct even
> though it has a public constructor (except through reflection) because
> User::Id is private; User::Id cannot be instantiated, used as a type hint=
,
> or even via `instanceof` outside of the User class itself. This example
> isn't practical but demonstrates something that is nearly impossible in
> previous versions of PHP, where all classes are essentially publicly
> accessible from anywhere within the codebase.
>
> As a number of inner classes will probably be used as DTOs, the RFC
> introduces a "short syntax" for declaring classes, which enhances
> expressiveness, even allowing the usage of traits, all in a single line:
>
> // declare a readonly Point, that implements Vector2 and uses the
> Evolvable trait
> readonly class Point(public int $x, public int $y) implements Vector2 use
> Evolvable;
>
> When combined with inner classes, it looks something like this:
>
> class Pixel {
>   public readonly class Point(public int $x, public int $y) implements
> Vector2 use Evolvable;
> }
>
> // Create a new pixel point with property $x and $y set to 0
> $p =3D new Pixel::Point(0, 0);
>
> There are far more details in the RFC itself, so please check it out. I'm
> quite excited to hear your thoughts!
>
> =E2=80=94 Rob
>
> PS. I know I tend to rush into things, but I want to make it clear that
> I'm not rushing this -- I've learned from my mistakes (thank you to those
> who have given me advice). I'm going to do this right.
>

I have read and reread this RFC, and I am struggling to see

1. What problem does this solve that anonymous classes
<https://www.php.net/manual/en/language.oop5.anonymous.php> do not?
2. As with any syntax change and new operator there needs to be very
careful consideration, do we need a new operation, or could `::` if the
parent is static or `->` if the class is initialized?
3. The idea that extending the parent class doesnt no inherit the child
classes doesnt make sense to me.
As then if you extend a parent class and call a function of that class
which could rely on the existence of an inner class, I can see a lot of
headaches caused by this exact scenario.
As a developer, if I extend a class, I expect the entire dependance of that
class to be inherited, otherwise the extending class won't work.

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<div dir=3D"ltr"><div dir=3D"ltr"><br></div><div class=3D"gmail_quote gmail=
_quote_container"><div dir=3D"ltr" class=3D"gmail_attr">On Wed, 5 Mar 2025 =
at 23:14, Rob Landers &lt;rob@bottled.codes&gt; wrote:<br></div><blockquote=
 class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px so=
lid rgb(204,204,204);padding-left:1ex"><div class=3D"msg-804317137376360737=
4"><u></u><div><div>Hello PHP Internals,<br></div><div><br></div><div>I&#39=
;d like to introduce my RFC for discussion:=C2=A0<a href=3D"https://wiki.ph=
p.net/rfc/short-and-inner-classes" target=3D"_blank">https://wiki.php.net/r=
fc/short-and-inner-classes</a><br></div><div><br></div><div>This RFC define=
s a short class syntax as well as the ability to nest classes inside anothe=
r class. This introduces an unprecedented amount of control, flexibility, a=
nd expressiveness over how objects are used and instantiated in PHP. There =
is a PR (<a href=3D"https://github.com/php/php-src/pull/17895" target=3D"_b=
lank">https://github.com/php/php-src/pull/17895</a>) that implements this f=
unctionality -- all test failures are related to different/new/incorrect er=
ror messages being generated. However, the core functionality exists to tak=
e for a test ride.<br></div><div><br></div><div>So, what do I mean by &quot=
;unprecedented amount of control&quot;? With this change, you can declare a=
n inner class as private or protected, preventing its usage outside of the =
outer class:<br></div><div><br></div><div>class User {<br></div><div>=C2=A0=
 private class Id {}<br></div><div><br></div><div>=C2=A0 public function __=
construct(public self::Id $id) {}</div><div>}<br></div><div><br></div><div>=
In the above example, the class `User` is impossible to construct even thou=
gh it has a public constructor (except through reflection) because User::Id=
 is private; User::Id cannot be instantiated, used as a type hint, or even =
via `instanceof` outside of the User class itself. This example isn&#39;t p=
ractical but demonstrates something that is nearly impossible in previous v=
ersions of PHP, where all classes are essentially publicly accessible from =
anywhere within the codebase.<br></div><div><br></div><div>As a number of i=
nner classes will probably be used as DTOs, the RFC introduces a &quot;shor=
t syntax&quot; for declaring classes, which enhances expressiveness, even a=
llowing the usage of traits, all in a single line:<br></div><div><br></div>=
<div>// declare a readonly Point, that implements Vector2 and uses the Evol=
vable trait</div><div>readonly class Point(public int $x, public int $y) im=
plements Vector2 use Evolvable;<br></div><div><br></div><div>When combined =
with inner classes, it looks something like this:</div><div><br></div><div>=
class Pixel {<br></div><div>=C2=A0 public readonly class Point(public int $=
x, public int $y) implements Vector2 use Evolvable;<br></div><div>}<br></di=
v><div><br></div><div>// Create a new pixel point with property $x and $y s=
et to 0</div><div>$p =3D new Pixel::Point(0, 0);<br></div><div><br></div><d=
iv>There are far more details in the RFC itself, so please check it out. I&=
#39;m quite excited to hear your thoughts!</div><div><br></div><div id=3D"m=
_-8043171373763607374sig121229152">=E2=80=94 Rob<br></div><div id=3D"m_-804=
3171373763607374sig121229152"><br></div><div><div>PS. I know I tend to rush=
 into things, but I want to make it clear that I&#39;m not rushing this -- =
I&#39;ve learned from my mistakes (thank you to those who have given me adv=
ice). I&#39;m going to do this right.</div></div></div></div></blockquote><=
div><br></div><div>I have read and reread this RFC, and I am struggling to =
see=C2=A0</div><div><br></div><div>1. What problem does this solve=C2=A0tha=
t <a href=3D"https://www.php.net/manual/en/language.oop5.anonymous.php">ano=
nymous classes</a>=C2=A0do not?</div><div>2. As with any syntax change and =
new operator there needs to be very careful consideration, do we need a new=
 operation, or could `::` if the parent is static or `-&gt;` if the class i=
s initialized?</div><div>3. The idea that extending the parent class doesnt=
 no inherit the child classes doesnt=C2=A0make sense to me.=C2=A0</div><div=
>As then if you extend a parent class and call a function of that class whi=
ch could rely on the existence of an inner class, I can see a lot of headac=
hes caused by this exact scenario.</div><div>As a developer, if I extend a =
class, I expect the entire dependance of that class to be inherited, otherw=
ise the extending class won&#39;t work.=C2=A0</div></div></div>

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